This invention concerns a unit to bear coaxial spindles: The unit to bear coaxial spindles according to this invention is applied advantageously to the textile industry and especially to spinning machines, twisters and two-for-one twisters.
Spindles on textile machines of the state of the art have a rotary shaft and are borne on bolsters with roller bearings or ball bearings.
The spindles are fitted above the spindle-bearing frames and are rotated at a speed of about 15,000 r.p.m. or more. The spindles are generally rotated by a belt which runs in the air.
There may be the situation of a plurality of spindles installed on the same spindle-bearing frame and cooperating with the same belt driven by one single motor or the situation of a shaft bearing a plurality of pulleys, each of which actuates a belt that actuates a spindle.
The spindle-bearing systems of the state of the art entail the problem of being unable to ensure that at least two spindles rotate at the same speed, for this same speed of rotation is necessary to achieve an excellent doubling of two yarns, for instance.
In fact, the spindles nowadays either are set in rotation individually by different motors or are driven by the same motor, to which they are connected by a belt, but neither of these two methods ensures a good synchronized rotation of two spindles.
Moreover, with the spindle-bearing systems of the state of the art the spindles are arranged on only one side, generally the upper side, of the machine, and this situation involves a great overall bulk of the machine owing to the great number of spindles fitted to a machine.
Furthermore, the spindle-bearing systems of the state of the art entail the drawback that owing to the high speed of rotation of the spindles the transmission belt vibrates in the air and generates unpleasant vibrations and noises.
These vibrations and noises are greater when one belt drives a plurality of spindles.
So as to obviate this noise, proposals have been made that the transmission belt should be eliminated and that each spindle should be driven by a high-frequency motor positioned also on the same axis as the spindle.
This system, however, increases the cost of the machine considerably and makes it uncompetitive on the market precisely owing to the necessity, determined by the state of the art, of having to use a high-frequency motor so as to be able to bring the spindles to the desired speed.